Modern vehicle concepts and structural designs of vehicles have a plurality of cavities which have to be sealed in order to prevent the ingress of moisture and contaminants, since the latter can result in corrosion from the inside on the corresponding body parts. This applies, in particular, to modern self-supporting body constructions in which a heavy frame construction is replaced by so-called “space frames”. With the latter, use is made of a lightweight, structurally solid chassis made of prefabricated hollow sections. Such constructions have, depending upon the specific system, a number of cavities which have to be sealed against the penetration of moisture and contaminants. These cavities include the upwardly extending A-, B- and C-pillars supporting the roof structure, the roof rail, portions of the fenders, or the sill. In addition, these cavities transmit airborne sound in the form of unpleasant vehicle running noises and wind noises. Therefore, such sealing measures also serve to reduce the noises and to enhance the comfort of traveling in the vehicle.
During the assembly of the car, these frame parts and body parts containing cavities are prefabricated from half-shell components which were joined at a later time by welding and/or adhesive bonding so as to form the closed hollow section. Within this specification, such half-shell components after joining are called “interconnected walls”, which surround the enclosed hollow section (“cavity”). With such a type of construction the cavity in the early body in white (“body shop”) state of a vehicle body is accordingly easily accessible, so that sealing and acoustically damping parts (sometimes referred to as “pillar fillers” or “cavity filler inserts”) can be fixed in this early phase of body construction by mechanical hanging, by insertion into appropriate holding devices, bores or by gluing or welding to the cavity walls.
Most modern baffles are designed to include a sealing material disposed on a support member or carrier. The carrier is generally manufactured from a rigid material, such as hard plastic, such that its shape approximates the shape of the cavity to be sealed. The carrier/sealing material combination is configured such that the carrier is inserted into a cavity. Typically, the sealing material is activated (thermally or chemically) to expand (or “foam”) after insertion into the cavity so that the sealing material forms a seal with the walls of the cavity. Thus, the expanded sealing material creates an airtight seal between the carrier and the walls of the cavity.
From WO 99/37506 a cavity sealing article is known which comprises a planar support member and a sealing member comprising a foamable polymer which surrounds in an intimate contact the support member and which is in plane with the support member. The foamable polymer comprises at least two layers which are in intimate contact and which are in the plane of the support member. The outer most layer of the sealing member comprises an un-cross linked foamable polymer and the inner layer comprises a cross linked foamable polymer.
WO 00/03894 A1 discloses a lightweight expandable baffle for sealing a cavity of a vehicle body at a predetermined cross section of the cavity. This baffle includes a rigid support plate having an outer periphery with a shape generally corresponding to but smaller than the shape of the cross section of the cavity. Said baffle comprises a heat expandable sealing material mounted to the outer periphery of the rigid support plate having an activation temperature range at which the material expands. The support plate is being formed of a material having a higher melting point than the activation temperature range of the sealing material. When activated, the sealing material expands radially from the rigid support plate to fill the cross-sectional cavity between the rigid support plate and the cavity walls.
WO 01/83206 A1 discloses a combined baffle and reinforcing assembly for use within the cavity of a structural member to dampen acoustic transmissions through the cavity and to provide reinforcement in a direction transverse to the longitudinal axis of the structural member. The combined assembly includes a synthetic carrier which comprises an interior area, a marginal rim and an attachment member preferably in a form of a clip suited for insertion to the corresponding hole in the wall of the structural member. The carrier is circumscribed by a continuous band of reinforcing material extending around the periphery of the carrier. The marginal rim of the carrier may include a base wall and a support flange for receiving the thermally expandable material thereon.
WO 01/71225 describes an expandable baffle part for sealing cavities in automobiles. This part comprises a thermally expandable sealing material that is able to expand at the temperatures of the e-coat bake oven. Moreover, the baffle part comprises a support which positions and fixes the expandable material at the predetermined point in the cavity until the thermal expansion sets in. The support further has at least one clip or a snap-action or plug-in device which is inserted under pressure into a corresponding bore or aperture in the hollow-space structure in order to fix the component.
In baffles according to the state of the art, the carrier for the thermally expandable sealing material is usually plate-like and flat. The baffle is inserted into the longitudinal cavity in a way that the plane of the carrier lies perpendicular to the longitudinal axis of the cavity, so that the cavity is bisected by the baffle.
Contrary to baffles, U.S. Pat. No. 4,901,395 describes a grommet for mounting in an opening in a compartment wall and including an elastomeric body having a passage therethrough for passing an elongated member through the compartment wall, such grommet comprising:                an axially extending central tubular portion of diameter less that the diameter of the compartment wall opening;        a flange portion integral with the central tubular portion and having a diameter greater than the diameter of the compartment wall opening to limit the extent of insertion of the central tubular portion into the compartment wall opening;        a retention means integral with the central tubular portion in axial spaced relation from the flange portion, said retention means having a free state dimension greater than the diameter of the central tubular portion and being yieldable to permit insertion of the tubular portion through the compartment wall opening and then returning to the free state condition to retain the grommet in loose fitting relation to the compartment wall;        and an annular ring of heat expandable material carried by the grommet, said annular ring expanding in response to occurrence of predetermined heat condition to fill the space between the grommet and the compartment wall and thereby seal the compartment wall opening.        
This grommet is different from the baffle of the present invention in at least the following aspects: The grommet is configured for sealing a (essentially two-dimensional) hole in a wall, not for sealing a (essentially three-dimensional) usually longitudinal cavity formed by interconnecting walls. It does not comprise a carrier plate (which is a flat object), but is an essentially three-dimensional object. The expandable material is not disposed along the outer perimeter of the plate, as it is the case for a baffle, but is essentially placed around the thinnest section of the grommet. The grommet has at least one flange portion which is larger than the opening to be sealed, whereas the baffle is essentially inside the cavity to be sealed, with the possible exception of fasteners which may penetrate a wall of the cavity for fixing the baffle prior to expanding the heat expandable material.
While the above mentioned baffles have been successfully employed to seal automotive body cavities against the intrusion of dust, water, carbon monoxide and to a certain extent noise, a need exists for an improved baffle with enhanced sound suppression capability.